BANGUI, Central African Republic (AP) — President Francois Bozize's government came under growing threat Monday as rebels vowing to overthrow him rejected appeals from the African Union to hold their advance and try to form a coalition government.

Meanwhile, dozens of troops from Republic of Congo arrived at sunset on New Year's Eve in Bangui, the capital, as part of an effort to step up the presence of a multinational regional military force.

After disembarking from their military aircraft, the group of about 120 men was headed toward the line between government forces and a coalition of four rebel groups, known as Seleka, north of Bangui.

The rebels have seized control of about 10 towns in less than a month's time, and now have moved within striking distance to the capital, a city of more than 700,000 people. The government has imposed a curfew of 7 p.m., leaving the streets largely empty on New Year's Eve.

Soldiers from Central African Republic and a regional military force are currently in Damara, about 45 miles from Bangui. The rebels, meanwhile, are holding the city of Sibut, which is about 115 miles away.

The rebels on Monday said they did not trust Bozize's offer to form a unity government, raising fears they could attempt a confrontation with government forces in the coming days.

"We are not convinced of the commitments made by President Bozize," said rebel spokesman Juma Narkoyo when reached by telephone. "Bozize has always spoken, but he never keeps his word."

The rebels said they would enter negotiations "only if the head of state releases all our relatives they have arrested without reason."

The rebels claim that Bozize has abducted more than a dozen of their family members. They warned if the president uses foreign troops to protect his government, they may continue their campaign toward the capital.

In response, the African Union told the rebels that if they seize power they will face sanctions and Central African Republic will be suspended from the organization.

Meanwhile, French President Francois Hollande welcomed the efforts by the AU and the group of neighboring states to find a negotiated solution. Hollande called for "opening a dialogue between CAR authorities and all the parties present, including the rebellion."

Hollande last week said his government would only protect French interests in CAR, but would not prop up the Bozize government.

Central African Republic has suffered many army revolts, coups and rebellions since gaining independence from France in 1960.

The rebels behind the current instability signed a 2007 peace accord allowing them to join the regular army, but insurgent leaders say the deal wasn't fully implemented.

Neighboring African countries have agreed to send more forces to support the Bozize government.

Representatives from the 10-nation Economic Community of Central African States, or ECCAS, agreed at a meeting in Gabon on Friday to send forces to CAR, but did not did not specify how many troops would be sent, or how quickly the military assistance would arrive.

The ECCAS states, with more than 500 soldiers via their regional peacekeeping force in Central Africa, warned the rebels over the weekend to halt their advances.

The neighboring Republic of Congo sent 120 troops from Brazzaville on Monday to bolster the regional force, according to a New Year's statement from Congo President Denis Sassou Nguesso. Troops from Gabon and Cameroon also were expected in the coming days to join extra forces already sent from Chad.

The regional forces are there to help stabilize the area but "will be forced to defend ourselves" if the rebel forces open fire, said Gabriel Enteha Ebia, the Republic of Congo's ambassador to Central African Republic.

The ongoing instability here already has prompted the United States to evacuate about 40 people, including the U.S. ambassador, from Bangui on an U.S. Air Force plane bound for Kenya, U.S. officials said on condition of anonymity because they weren't authorized to discuss the operation.

The United States has special forces troops in the country who are assisting in the hunt for Joseph Kony, the fugitive rebel leader of another rebel group known as the Lord's Resistance Army. The U.S. special forces remain in the country, the U.S. military's Africa Command said from its headquarters in Stuttgart, Germany.

The evacuation of the U.S. diplomats came after criticism of how the U.S. handled diplomatic security before and during the attack on its consulate in Benghazi, Libya, on Sept. 11. The ambassador and three other Americans were killed in that attack.

China announced Monday that it is evacuating its 300 citizens from CAR, although its embassy staff will stay.

French diplomats have remained in Bangui, despite a violent demonstration outside its embassy last week. Dozens of protesters, angry at France's lack of help against rebel forces, threw rocks at the French Embassy in Bangui and stole a French flag.

CAR, a landlocked nation of 4.4 million people, is one of the poorest countries in the world. The current president himself came to power nearly a decade ago in the wake of a rebellion in this resource-rich yet deeply poor country. Despite Central African Republic's wealth of gold, diamonds, timber and uranium, the government remains perpetually cash-strapped.